Fludrocortisone Acetate

Steroidal drug with glucocorticoid action and high activity as mineralocorticoid.
Systemic administration: oral route. Topical administration: creams as dermatologic compounds and eye drops for ophthalmologic use.
Indicated as replacement therapy in Adrenal Insufficiency (Addison’s Disease) and "salt-losing" Congenital Adrenal Hyperplasia.

At latest update relevant published data were not found on excretion into breast milk.
Other corticosteroids are know to be excreted into breastmilk in small amounts.
Since the goal of treatment is to keep the mother within normal plasma hormone ranges, by monitoring adequately through analytical controls to make sure the mother is receiving a correct dose, it would neither interfere with breastfeeding nor would be harmful to the infant. Take as lowest effective dose as possible with follow-up the infant for hypo-adrenal signs.

The small dose used along with a poor passage to plasma of most ophthalmologic and topical dermatologic preparations makes it very unlikely that a significant excretion into breastmilk would occur.
Do not apply on the breast to prevent ingestion by the infant; otherwise, do it just after a meal and clean the nipple thoroughly with water before the next feed. Mineral-corticoid poisoning occurred in an infant after long-term application of a corticoid cream on the nipple (De Stefano 1983).